Biology subjects

Chamolly, A.

Publications and source records attributed to Chamolly, A..

5 recordsLinked to original sources

bioRxiv2025

Wnt and Nodal asymmetries stratify mouse laterality phenotypes in the absence of node flow

Left-right symmetry breaking in mice is considered to occur via node leftward fluid flow. The molecular cascade within the node has been reconstructed at high resolution. However, its importance for organogenesis remains poorly understood. Here we show in mutants for the motile cilium component CCDC40 that 70% of mice develop normal situs at birth despite abrogation of node flow. The discrete morphospace output, including situs inversus totalis and heterotaxy with left isomerism, supports a novel model of symmetry-breaking, in which node flow only biases asymmetry orientation, while another mechanism, potentially self-amplifying, generates it. Longitudinal, quantitative and paired transcriptomic analyses uncover the molecular signature of laterality clusters, highlighting WNT in addition to NODAL pathway asymmetry. We identify asymmetry of cardiopulmonary progenitors, the disruption of which is associated with combined heart and lung defects in mutants. Our work refines the role of the node in the establishment of asymmetry.

developmental biology↗

bioRxiv2025

Direct measurements of active forces and material properties unveil the active mechanics of early embryogenesis

Despite progress in probing tissue mechanics, direct long-term measurements in live embryonic epithelia are lacking. This limits our understanding of amniote embryonic morphogenesis, which takes place over hours or days. Here, we introduce a combined technological and analytical framework to directly measure active forces and material properties in developing quail embryos, in a minimally invasive way. We find that the embryonic epithelium behaves elastically on short timescales with a modulus [~] 2 nN {middle dot} m-1 but flows over longer timescales with a viscosity [~] 4 N {middle dot} s {middle dot} m-1, and that both properties are under active regulation. Notably, we demonstrate that cell division is an active epithelial fluidizer, with division rates correlating with tissue fluidity. This fluidization is crucial for the emergence of the primary embryonic axis, which we show is shaped by a force [~] 2 N. Altogether, our approach delivers a complete and quantitative view of early embryonic mechanics, and opens new avenues for biomechanical studies in live embryos and tissues.

developmental biology↗

bioRxiv2024

A tension-induced morphological transition shapes the avian extra-embryonic territory

The segregation of the extra-embryonic lineage is one of the earliest events and a key step in amniote development. Whereas the regulation of extra-embryonic cell fate specification has been extensively studied, little is known about the morphogenetic events underlying the formation of this lineage. Here, taking advantage of the amenability of avian embryos to live and quantitative imaging, we investigate the cell- and tissue-scale dynamics of epiboly, the process during which the epiblast expands to engulf the entire yolk. We show that tension arising from the outward migration of the epiblast border on the vitelline membrane stretches extra-embryonic cells, which reversibly transition from a columnar to squamous morphology. The propagation of this tension is strongly attenuated in the embryonic territory, which concomitantly undergoes fluid-like motion, culminating in the formation of the primitive streak. We formulate a simple viscoelastic model in which the tissue responds elastically to isotropic stress but flows in response to shear stress, and show that it recapitulates the flows and deformation of both embryonic and extra-embryonic tissues. Together, our results clarify the mechanical basis of early avian embryogenesis and provide a framework unifying the divergent mechanical behaviors observed in the contiguous embryonic and extra-embryonic territories that make up the epiblast. HighlightsO_LIThe extra-embryonic region expands radially during epiboly C_LIO_LICell area increase accounts for the rapid extra-embryonic expansion C_LIO_LIEpiboly-induced tension reversibly stretches extra-embryonic cells C_LIO_LIA simple viscoelastic model recovers the morphogenesis of the entire epiblast C_LI

developmental biology↗

bioRxiv2023

Controlling confined collective organisation with taxis

Biased locomotion is a common feature of microorganisms, but little is known about its impact on self-organisation. Inspired by recent experiments showing a transition to large-scale flows, we study theoretically the dynamics of magnetotactic bacteria confined to a drop. We reveal two symmetry-breaking mechanisms (one local chiral and one global achiral) leading to self-organisation into global vortices and a net torque exerted on the drop. The collective behaviour is ultimately controlled by the swimmers microscopic chirality and, strikingly, the system can exhibit oscillations and memory-like features.

biophysics↗

bioRxiv2021

Self-organized tissue mechanics underlie embryonic regulation

Early amniote development is a highly regulative and self-organized process, capable to adapt to interference through cell-cell interactions, which are widely believed to be mediated by molecules. Analyzing intact and mechanically perturbed avian embryos, we show that the mechanical forces that drive embryogenesis self-organize in an analog of Turings molecular reaction-diffusion model, with contractility locally self-activating and the ensuing tension acting as a long-range inhibitor. This mechanical feedback governs the persistent pattern of tissue flows that shape the embryo and steers the concomitant emergence of embryonic territories by modulating gene expression, ensuring the formation of a single embryo under normal conditions, yet allowing the emergence of multiple, well-proportioned embryos upon perturbations. Thus, mechanical forces are a central signal in embryonic self-organization, feeding back onto gene expression to canalize both patterning and morphogenesis.

developmental biology↗